apart. The spread between legs must be no more than
two-thirds nor less than one-half the length of a leg,
Small tripods, or those lashed according to the first
procedure given in the preceding section, may be
raised by hand. Here are the main steps.
Start by raising the top ends of the three legs
about 4 feet, keeping the butt ends of the legs on the
ground. Now, cross the tops of the two outer legs, and
position the top of the third or center leg so that it rests
on top of the cross.
A sling for the hoisting tackle can be attached
readily by first passing the sling over the center leg,
and then around the two outer legs at the cross. Place
the hook of the upper block of a tackle on the sling,
and secure the hook by mousing.
The raising operation can now be completed. To
raise an ordinary tripod, a crew of about eight maybe
required. As the tripod is being lifted, spread the legs
so that when it is in the upright position, the legs will
be spread the proper distance apart. After getting the
tripod in its final position, lash the legs near the
bottom with line or chain to keep them from shifting
(figure 4-40). Where desirable, a leading block for
the hauling part of the tackle can be lashed to one of
the tripod legs, as indicated in figure 4-40.
In erecting a large tripod you may need a small
gin pole to aid in raising the tripod into position. To
erect a tripod lashed according to the first procedure
described in the preceding section, you first raise the
tops of the legs far enough from the ground to permit
spreading them apart. Use guys or tag lines to help
hold the legs steady while they are being raised. Now,
with the legs clear of the ground, cross the two outer
legs and place the center leg so that it rests on top of
the cross. Then, attach the sling for the hoisting
tackle. Here, as with a small tripod, simply pass the
sling over the center leg and then around the two outer
legs at the cross.
LEARNING OBJECTIVE: Upon completing
this section, you should be able to determine
the proper usage of wood and prefabricated
As the working level of a structure rises above the
reach of crew members on the ground or deck,
temporary elevated platforms, called scaffolding, are
erected to support the crew members, their tools, and
There are two types of scaffolding in use
today-wood and prefabricated. The wood types
include the swinging scaffold, which is suspended
from above, and the pole scaffold, which is supported
on the ground or deck.
The prefabricated type is
made of metal and is put together in sections, as
SWINGING SCAFFOLD CONSTRUCTION
The simplest type of a swinging scaffold consists
of an unspliced plank that is made from 2-by-8-inch
Hangers should be placed
between 6 and 18 inches from the ends of the plank.
The span between hangers should not exceed 10 feet.
Make sure that the hangers are secured to the plank to
stop them from slipping off. Figure 4-42 shows the
construction of a hanger with a guardrail. The
guardrail should be made of 2-by-4-inch material
between 36- and 42-inches high. A midrail, if
required, should be constructed of 1-by-4 lumber.
Figure 4-42.Typical hanger to use with plank scaffold.